Latest News & Research: 23 April 2019

This week: HIIT linked to increased injury incidence • Speedy weight lifting may mean longer life • Breast milk and childhood obesity prevention


HIIT linked to increased injury incidence

People who engage in high-intensity interval training are at greater risk for injury, especially in the knees and shoulders, a Rutgers study found.

The study, which appears in the Journal of Sports Medicine and Physical Fitness, acknowledged that while this type of training is effective in improving cardiorespiratory fitness, boosting energy and promoting lean muscle mass and fat loss, it also increases injury risk.

‘These workouts are marketed as ‘one size fits all.’ However, many athletes, especially amateurs, do not have the flexibility, mobility, core strength and muscles to perform these exercises’ said Joseph Ippolito, a physician in the Department of Orthopaedics at Rutgers New Jersey Medical School.

Analysing records in the National Electronic Injury Surveillance System from 2007 to 2016, the researchers found 3,988,902 injuries resulting from exercise equipment, such as barbells, kettlebells and boxes, or calisthenics, such as burpees, push-ups and lunges, that are common to these programs. Most injuries involved knees, ankles and shoulders. White males aged 20 to 39 were most injured.

The researchers found a steady increase of an average of 50,944 injuries per year, which rose alongside the growth in interest in the workouts as determined by the number of Google searches during the years studied. During this decade, they found a significant increase in nerve damage, internal organ injuries, concussions, puncture wounds, dislocations and strains and sprains.

Athletes who perform these workouts without supervision are at increased risk for injury from poor form and muscle overuse. ‘There is strong evidence that these types of injuries – specifically from repetitive overload at the knee – can lead to osteoarthritis’ said Ippolito.

People who are new to these workouts should speak with their physicians first, and more experienced athletes should learn how to minimise preventable injuries, the researchers recommended. Athletic trainers, physical therapists and fitness instructors should ensure athletes are conditioned, use proper form and understand the recovery phase.

‘We certainly do not want to discourage people from this type of exercise because of its numerous health benefits, but recommend that they understand the pre-existing conditions and physical weaknesses that may predispose them to injury’ said co-author Nicole D. Rynecki, a student at the medical school.

Since knee and ankle sprains and strains were the most common injuries from high-intensity interval workouts, people should do neuromuscular training – especially those that focus on strength, jumping and balance – and pre-strengthening programs to improve flexibility before starting high-intensity interval exercises, Rynecki said: ‘Exercises such as stretches that can increase range of motion and strengthen rotator cuff muscles are important, especially for older people and those who are predisposed to rotator cuff tears’ she noted.

Source: Rutgers University



Speedy weight lifting may mean longer life

Prolong your life by increasing your muscle power – that’s the main message of a new Brazilian study.

‘Rising from a chair in old age and kicking a ball depend more on muscle power than muscle strength, yet most weight bearing exercise focuses on the latter’ said study author Professor Claudio Gil Araújo, director of research and education, Exercise Medicine Clinic – CLINIMEX, Rio de Janeiro, Brazil; ‘Our study shows for the first time that people with more muscle power tend to live longer.’

Power depends on the ability to generate force and velocity, and to coordinate movement. In other words, it is the measure of the work performed per unit time (force times distance); more power is produced when the same amount of work is completed in a shorter period or when more work is performed during the same period. Climbing stairs requires power – the faster you climb, the more power you need. Holding or pushing a heavy object (for example a car with a dead battery) needs strength.

Professor Araújo said ‘Power training is carried out by finding the best combination of speed and weight being lifted or moved. For strength training at the gym most people just think about the amount of weight being lifted and the number of repetitions without paying attention to the speed of execution. But for optimal power training results, you should go beyond typical strength training and add speed to your weight lifts.’

Muscle power gradually decreases after 40 years of age. ‘We now show that power is strongly related to all-cause mortality. But the good news is that you only need to be above the median for your sex to have the best survival, with no further benefit in becoming even more powerful’ said Professor Araújo.

The study enrolled 3,878 non-athletes aged 41–85 years who underwent a maximal muscle power test using the upright row exercise between 2001 and 2016. The average age of participants was 59 years, 5% were over 80, and 68% were men. The highest value achieved after two or three attempts with increasing loads was considered the maximal muscle power and expressed relative to body weight (i.e. power per kg of body weight). Values were divided into quartiles for survival analysis and analysed separately by sex.

During a median 6.5-year follow-up, 247 men (10%) and 75 women (6%) died. Median power values were 2.5 watts/kg for men and 1.4 watts/kg for women. Participants with a maximal muscle power above the median for their sex (i.e. in quartiles three and four) had the best survival. Those in quartiles two and one had, respectively, a 4–5 and 10–13 times higher risk of dying as compared to those above the median in maximal muscle power.

Professor Araújo noted that this is the first time the prognostic value of muscle power has been assessed. Previous research has focused on muscle strength, primarily using the handgrip exercise. The upright row exercise was chosen for the study because it is a common action in daily life for picking up groceries, grandchildren, and so on. The researchers are currently examining the link between muscle power and specific causes of death including cardiovascular disease and cancer. He added; ‘Doctors should consider measuring muscle power in their patients and advise more power training.’

Source: European Society of Cardiology



Breast milk and childhood obesity prevention

New research suggests the composition of breast milk in normal weight mothers differs from that of overweight mothers, and that variations in small molecule metabolites found in breast milk are possible risk factors for childhood obesity. The new research is published online in The American Journal of Clinical Nutrition.

It’s known that maternal obesity is one of the strongest predictors of childhood obesity. ‘Childhood obesity increases risk for type 2 diabetes, and a host of other health complications. Our aim is to identify the earliest risk factors that predict obesity in children’ said study lead author Elvira Isganaitis, MD, MPH, a pediatric endocrinologist at Joslin Diabetes Center; ‘We know that one of those factors is nutritional exposures in the postnatal period.’

In collaboration with colleagues from the University of Oklahoma Health Sciences Center and the University of Minnesota, the researchers analysed breast milk content and infant body measures (fat and muscle) at both one month and six months of age in 35 mother-infant pairs. Mothers were classified by pre-pregnancy body mass index (BMI) less than 25 (normal) or greater than 25 (overweight/obese).

Prior to 2010, there wasn’t much known about the composition of human breast milk beyond basic macronutrients, says study senior author David Fields, PhD, an associate professor at the University of Oklahoma Health Sciences Center and an expert in pediatric diabetes; ‘Our research digs deeper into the composition of breast milk, beyond simple carbohydrates, protein and fat.’

Using the technological advance of metabolomics analyses (a technique for large-scale studies of small molecules involved in metabolism), Isganaitis and collaborators analysed the concentration of 275 individual small molecule metabolites in breast milk. The aim was to identify the molecular features of breast milk according to the mother’s weight status (normal versus overweight/obese) and then to determine if any differences predicted excess weight in the first months of the infant’s life.

At one month of age, 10 metabolites were found that differentiated overweight/obese mothers from lean mothers. Of those, four were identified as nucleotide derivatives and three were identified as complex carbohydrates called oligosaccharides, which may alter the gut microbiota. At six months of age, the analysis revealed that 20 metabolites differed in overweight versus lean women. Additionally, milk adenine in obese mothers was associated with greater weight gain in infants.

While only modest differences in the milk composition between obese and lean mothers were found (10 at one month and 20 at six months, out of 275), this is the first in-depth study where we could see which substances in breast milk were more abundant in women who were overweight and which ones were lower, said Isganaitis; ‘Our findings suggest that a specific mix of factors --- nucleotide derivatives and complex carbohydrates -- could be therapeutic targets to improve the profile of breast milk and possibly protect children from obesity’.

This research is a step forward in understanding that a mother’s weight status and health can influence breast milk, and, in turn, impact the health of the baby. Fields, who started the clinical research project at the University of Oklahoma Health Sciences Center, explains that by identifying and profiling molecules that differ between normal and overweight mothers, the researchers are laying the foundation for interventions, diet, pharmacological or exercise, that would improve the quality of breast milk in overweight and obese mothers.

Breastfeeding is a very beneficial behavior for both mothers and their children, said Isganaitis; ‘Breastfeeding should be promoted and supported. Ultimately, we would like to identify the metabolic pathways that allow breast milk to be beneficial in terms of infant weight gain, and other child health outcomes. The hope is that this data could also inform ways to make baby formula more protective in terms of future childhood obesity risk.’

Source: Joslin Diabetes Center